Outboard engines generally comprise an end for the fastening to the transom of a watercraft on which the engine is mounted so as to rotate around a substantially vertical steering axis.
The steering device comprises a closed hydraulic circuit with at least one pump actuated by steering means, such as a steering wheel, a rudder or the like, while the cylinder is slidably mounted on at least one rod coaxial thereto and sealingly protruding from at least one head of the actuating cylinder and carries a separating piston that divides the cylinder into two variable-volume chambers.
Each of the two chambers has at least one inlet/outlet for the hydraulic fluid, each connected to one of two inlet/outlet of the pump, and a sealing head for the relative sliding between cylinder and rod, the sealing head being integral with the cylinder itself.
Furthermore the rod is connected to a fastening bracket to fasten the cylinder to the engine, in a not slidable manner and in such a way as to allow the relative rotation of the engine with respect to the transom along an axis parallel to the axis of the rod.
Finally, there is a tiller arm fastened to the engine and integral with the cylinder, for steering the engine.
The above described configuration is the common configuration of the double-acting hydraulic actuators currently known and widely used.
This invention actually concerns hydraulic cylinders, regardless of their specific design, whether they are cylinders as described above, unbalanced cylinders or any other cylinder known in the state of the art.
Typical examples of such actuators are described in document EP 1488996 of the Applicant.
The various components of the known actuator cylinders are therefore widely used and tested in order to optimize the operation of the cylinders.
Although these devices perform their function satisfactorily, they have some drawbacks.
One of the most common drawbacks is the difficulty of disassembling the rod from the bracket fastening the cylinder to the engine. In fact, this fastening is usually carried out by nuts cooperating with threaded appendages obtained at the ends of the rod. The bracket has L-shaped end elements provided with corresponding through holes in which the threaded ends are inserted to be tightened by the nut.
The rod and cylinder are free to move relative to each other, so that the aforementioned fastening means are the only rotational constraint of the rod. Therefore, when disassembling the cylinder, a clamp tool must be used to allow the rod to be clamped when the bracket fastening nuts are unscrewed. On the other hand, the grip of this tool can damage the surface of the rod, resulting in a loss of seal between the cylinder and the rod.